When thin films are deposited in semiconductor device fabrication, seams, keyholes, and other anomalies that include corners at the exposed surface of the film may be formed in the films above recesses in the underlying device. Existing chemistries of isotropic etch (e.g., wet etch or cleaning) processes, such as hydrofluoric acid (HF) (e.g., 100:1 water:HF), buffered oxide etchants (BOE) (e.g., 20:1 water:BOE), and etchants that include ammonium fluoride, dilute HF, and phosphoric acid, will enter the recesses or crevices of such anomalies and remove material from corners of the structure or film bounding the recesses or crevices at a faster rate than the material is removed from smoother (e.g., more planar), exposed, nonrecessed surfaces of the film or other structure. Such undesired amplification of anomalies may occur even when films or other structures that include seams, keyholes, and other anomalies have been polished or planarized, and even when such anomalies are not visible by modern imaging techniques, such as electron microscopy. The increased rate at which material is removed by isotropic etchants from corners may result in amplification of seams, keyholes, and similar anomalies, which enhances the occurrence of nonplanarities in the topography of the etched film or other structure. This phenomenon is particularly undesirable in state-of-the-art semiconductor devices, in which circuit, or “line,” widths are about 50 nm or less. These detrimental effects will continue to increase with continued decreases in feature dimensions of state-of-the-art semiconductor devices.
While anisotropic etch (e.g., dry etch) processes may be used to avoid the amplification of seams, keyholes, and similar anomalies into larger surface nonplanarities as material is removed from a structure or film, use of such processes undesirably increases processing time and costs.
Accordingly, wet etchants and wet etch processes that reduce, minimize, or eliminate amplification of seams, keyholes, and similar anomalies are desired.